Flat panel displays, such as liquid crystal displays (LCDs), plasma display panels (PDPs), electroluminescent displays (ELDs) and vacuum fluorescent displays (VFDs), are popularly commercialized due to their small size and less power consumption. Among these flat panel displays, the LCD is the most popular in development owing to its good performance and less power consumption, even though it has many disadvantages.
Contrary to the prior monolithic transistor formed on a semiconductor substrate, a thin film transistor (TFT) is fabricated by stacking several films over a substrate. Therefore, the TFT possesses a simpler and easy-fabricated structure than the prior monolithic transistor. For this reason, the TFT has widely served as a switch device of, for example, large-size electric devices (e.g., LCDs). In order to make the image of TFT-LCD to be consistently, the signal voltage input to the data lines must be held constantly in a particular period of time before the next signal is being input. Consequently, for enhancing the image quality of LCD, a storage capacitor is generally disposed in each pixel region.
FIG. 1 depicts a pixel layout of a prior LCD. As shown in FIG. 1, a plurality of scanning g lines 2 and data lines 5 arranged in array are formed over a substrate 1. A pixel region denotes a region surrounded by two adjacent scanning lines and two adjacent data lines. Each pixel region has a pixel electrode 4 disposed therein. The pixel electrode 4 is connected to a semiconductor layer 3 by a drain 7. The semiconductor layer 3 is formed on the scanning line 2 and connected to the data line 5 by a source. Besides, each pixel region has a capacitor electrode 10 disposed therein.
Since there are some demands, for example, better displaying brightness and saving power consumption, for the LCD, the higher aperture ratio is better. For accomplishing higher aperture ratio (i.e., the ratio of transparent area), an LCD in which pixel electrodes overlap data lines has been developed. However, the construction in which the pixel electrodes overlap the data lines invites an increased coupling capacitance Csd between the pixel electrodes and data lines. If the coupling capacitances Csd1/Csd2 respectively generated from the both sides of the pixel electrode and adjacent data lines are held coherently, ill influence on the image quality caused by the coupling capacitance would be effectively reduced. Nevertheless, the pixel electrodes and the data lines are greatly different in photolithographic processes, so it is very hard to make the pixel electrodes precisely aligned to the data lines. Hence, when the misalignment occurs, the coupling capacitances Csd1/Csd2 respectively generated from the both sides of the pixel electrode and adjacent data lines cannot be held coherently, that leads uneven displaying on the LCD.
Thus, U.S. Pat. No. 6,633,360 B2 discloses an LCD having S-shaped data lines 8, as shown in FIG. 2, for solving the problem due to variations in the coupling capacitance Csd caused by misalignment of the aforementioned process. However, for considering the assembling precision to prevent light from leaking, a black matrix (BM) 9 disposed over the color filter (CF) substrate is generally designed to be wide enough to completely cover the S-shaped data lines 8. But it will induce that the aperture ratio of the LCD is severely lowered. In addition, the capacitor electrode 10 is generally formed by opaque electrically conductive metal, for example, aluminum, chromium, tantalum of molybdenum, so as to further lower the aperture ratio (i.e., the ratio of transparent area).
As described above, there is an urgent need to solve the problem of the LCD and the TFT substrate therefore with respect to variations in the coupling capacitance Csd and decreased aperture ratio.